[PATCH] D126699: [CMake] Skip linker check if the LLVM_LINKER_WORKS is set

[Pavel Samolysov via Phabricator via llvm-commits]

psamolysov created this revision.
psamolysov added reviewers: phosek, mstorsjo, ruiu, RKSimon, thieta, ldionne.
psamolysov added a project: LLVM.
Herald added a subscriber: mgorny.
Herald added a project: All.
psamolysov requested review of this revision.
Herald added a subscriber: llvm-commits.

CMake has a set of 'CMAKE_<LANG>_COMPILER_WORKS' variables to skip checking
of the corresponding compiler during the configuration phase what is used by
LLVM to build runtimes: the `llvm/runtimes/CMakeLists.txt` file contains calls
of the `llvm_ExternalProject_Add` function to build the runtime components and
on these calls all the 'CMAKE_<LANG>_COMPILER_WORKS' variables are set to
 'ON'.

The patch introduces a new similar variable 'LLVM_LINKER_WORKS' that is used
to skip checking of the used linker if the 'LLVM_USE_LINKER' variable is set.
The check should be skipped during building runtime components for non-host
environments: at this time the required libraries (libunwind, builtins, crt,
etc.) are not ready and the check will false positive fail.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126699

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake
  llvm/runtimes/CMakeLists.txt


Index: llvm/runtimes/CMakeLists.txt
===================================================================
--- llvm/runtimes/CMakeLists.txt
+++ llvm/runtimes/CMakeLists.txt
@@ -245,6 +245,7 @@
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
                                       -DLLVM_BUILD_TOOLS=${LLVM_BUILD_TOOLS}
+                                      -DLLVM_LINKER_WORKS=ON
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
@@ -355,6 +356,7 @@
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
+                                      -DLLVM_LINKER_WORKS=ON
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -302,13 +302,15 @@
 endif()
 
 if( LLVM_USE_LINKER )
-  set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fuse-ld=${LLVM_USE_LINKER}")
-  check_cxx_source_compiles("int main() { return 0; }" CXX_SUPPORTS_CUSTOM_LINKER)
-  if ( NOT CXX_SUPPORTS_CUSTOM_LINKER )
-    message(FATAL_ERROR "Host compiler does not support '-fuse-ld=${LLVM_USE_LINKER}'")
+  if( NOT DEFINED LLVM_LINKER_WORKS )
+    set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fuse-ld=${LLVM_USE_LINKER}")
+    check_cxx_source_compiles("int main() { return 0; }" CXX_SUPPORTS_CUSTOM_LINKER)
+    if ( NOT CXX_SUPPORTS_CUSTOM_LINKER )
+      message(FATAL_ERROR "Host compiler does not support '-fuse-ld=${LLVM_USE_LINKER}'")
+    endif()
+    set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
   endif()
-  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
   append("-fuse-ld=${LLVM_USE_LINKER}"
     CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
 endif()


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